From: Maxime Coquelin <maxime.coquelin@redhat.com>
To: wangzengyuan <wangzengyuan@huawei.com>, "dev@dpdk.org" <dev@dpdk.org>
Cc: "chenbo.xia@intel.com" <chenbo.xia@intel.com>,
"zhangxu (BA)" <jesse.zhangxu@huawei.com>,
luyicai <luyicai@huawei.com>,
wangyunjian <wangyunjian@huawei.com>
Subject: Re: dpdk: Inquiry about vring cleanup during packets transmission
Date: Tue, 30 May 2023 11:48:27 +0200 [thread overview]
Message-ID: <1d846873-9bc5-814f-b0a7-2375f0a332a6@redhat.com> (raw)
In-Reply-To: <cbb8e8c33fcd4661a844a9993d29f9fa@huawei.com>
Hello,
On 5/27/23 09:08, wangzengyuan wrote:
> Hi,
>
> I am writing to inquire about the vring cleanup process during
> packets transmission.
>
> In the virtio_xmit_pkts function, there is the following code:
>
> nb_used = virtqueue_nused(vq);
>
> if (likely(nb_used > vq->vq_nentries - vq->vq_free_thresh))
>
> virtio_xmit_cleanup(vq, nb_used);
>
> In other words, cleaning is performed when the number of items used in
> the vring exceeds (vq->vq_nentries - vq->vq_free_thresh). In the case of
> an vring size of 4096, at least (4096-32) items need to be cleaned at
> once, which will take a considerable amount of time.
>
> I'm curious why not clean up fewer items each time to avoid taking up
> too much CPU time in one transmission. Because during the debugging
> process, I found that cleaning up thousands of items at once takes up a
> considerable amount of time.
>
> As I am not familiar with this process, I would appreciate it if you
> could provide me with some information on what its purpose is.
Both the Tx and Rx queues free threshold are configurable via ethdev
APIs:
int rte_eth_tx_queue_setup(uint16_t port_id, uint16_t tx_queue_id,
uint16_t nb_tx_desc, unsigned int socket_id,
const struct rte_eth_txconf *tx_conf);
int rte_eth_rx_queue_setup(uint16_t port_id, uint16_t rx_queue_id,
uint16_t nb_rx_desc, unsigned int socket_id,
const struct rte_eth_rxconf *rx_conf,
struct rte_mempool *mb_pool);
As you are using large rings, your application may use above APIs to set
more appropriate values.
Regards,
Maxime
> Best regards,
>
> Zengyuan Wang
>
prev parent reply other threads:[~2023-05-30 9:48 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-05-27 7:08 wangzengyuan
2023-05-30 9:48 ` Maxime Coquelin [this message]
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